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In a context of climate change characterized by rising temperatures, increased greenhouse gases and frequent droughts, the Sahel is presented as one of the most vulnerable areas to the adverse effects of climate change. The Sahel is presented as one of the most vulnerable areas to the adverse effects of climate change. The objective of this study is to assess the above-ground biomass and carbon stock of three Sahelian species: Acacia raddiana tortilis (Forsk.) hayne ssp. raddiana (savi) Brenan, Acacia senegal (L.) Willd and Balanites aegyptiaca (L.). The study was carried out in northern Senegal commonly known as Ferlo. Biomasses of the populations of the three target species were first assessed by harvesting the entire epigenetic part of the species and then modelled by correlation using dendrometric parameters measured on each individual of the sample. Two models, mono-specific and multi-species, were used. The results obtained showed that the diameter at breast height (x) and the parameter best correlated to the epigeal biomass (y). The dry biomass of woody plants was 31.4 ± 15.2 kg/tree for B. aegyptiaca, 30.6 ± 13.2 kg/tree for A. senegal and 26.2 ± 11.1 kg/tree for A. raddiana; i.e. carbon equivalents of 14.75 - 14.38 - 12.31 kg/tree respectively. The amount of carbon contained in the above-ground woody biomass is estimated at 4.48 t/ha. The carbon equivalent, atmospheric CO2 is estimated at 16.44 tons of CO2/ha and based on the actual density of Ferlo (108.08 ± 49.79 ind/ha) the sequestered carbon of the area is estimated at 1777.008 tons of CO2. The comparison between the models developed in this study and the multispecific or mono-specific models from the literature showed substantial differences. This study contributes to a better understanding of the contribution of Sahelian woody species to carbon sequestration and the results could be used in the framework of adaptation to climate change.

The objective of this study is to analyze the dendrochronological potential of two Sahelian species (B. senegalensis and S. birrea) and to evaluate the relationships between their growth rings and the climate. The study was conducted in 2016 in the Ferlo area of Senegal. The biological material consists of wood slices, taken from the trunks of these adult woody species at 0.30 m and 1.30 m from the ground after they have been felled. The technique used to examine the slices consists in identifying their rings, establishing their structures, inter-dating them and studying the relationship between the identified rings and climatic factors. The results showed that the species had thin, clear, highly visible and sharp rings. The limit of growth is marked by a line of parenchyma. Intradatation series carried out on the chronologies made it possible to estimate the ages of the individuals, which vary from 10 to 38 years for B. senegalensis and from 29 to 50 years for S. birrea. Their average growth rates are estimated at 0.906 mm/year and 0.89 mm/year respectively. The chronological sequences are 29 years (1987-2016) for B. senegalensis and 38 years (1964-2012) for S. birrea. The results revealed that there is no significant correlation between the growth chronologies of B. senegalensis and the climatic regressors (temperature and precipitation). In contrast, the ring-climate relationship shows that in S. birrea winter precipitation positively influences ring growth while temperature has no effect on ring growth in this species. This study provides a better understanding of the response of forest ecosystems to possible climate change, particularly in the current context of sustainable forest management.

L'objectif de cette étude est d’évaluer les effets de l'application de différents fertilisants organiques (fumier de vache, litières de Balanites aegyptiaca (L.) Del., Boscia senegalensis (Pers.) Lam. ex Poir. et Sclerocarya birrea (A. Rich.) Hochst) sur les paramètres de croissance et de rendement de la variété F1 Mongal de la tomate (Solanum lycopersicum L.) en conditions semi-contrôlées. L’étude a été effectuée à la ferme agricole de l’Université Gaston Berger de Saint Louis au Nord du Sénégal entre avril et juin 2018. Le dispositif expérimental utilisé est en blocs aléatoires randomisés avec quatre (04) répétitions, huit (08) traitements et trois (03) doses (0,2%, 0,5% et 0,8%). Les traitements appliqués sont : T0 (témoin sans apport de fertilisant), T1 (litière de Balanites aegyptiaca), T2 (litière de Boscia senegalensis), T3 (litière de Sclerocarya birrea), T4 (fumier), T5, T6 et T7 (mélange à proportion égale (½+ ½) de fumier et chacune des trois (03) litières). Après application des différents fertilisants organiques, une durée de décomposition de 15 jours a été observée avant semis dans des pots de 1,5 kg. Après 60 jours de croissance, les résultats obtenus ont montré que les effets sur la croissance de la tomate varient en fonction de la dose et de la qualité de la matière organique apportée. Les litières de B. senegalensis appliquées seules ou en combinaison avec le fumier et la litière B. aegyptiaca utilisée seule ont amélioré significativement certains des paramètres étudiés (hauteur, surface foliaire, biomasse sèche aérienne et couleur du feuillage) aux doses de 0,5% et 0,8%. Les meilleurs effets ont été induits par la plus forte dose (0,8%) de B. senegalensis. La litière de S. birrea n’a pas eu d’effets significatifs sur les paramètres de croissance et de rendements de la tomate. Le fumier n’a montré aucun effet sur les paramètres de croissance de la tomate par rapport au témoin sans fertilisant. Ainsi, la litière de B. senegalensis dans les conditions de cet essai, a montré un grand potentiel pour l’amélioration des paramètres de croissance et de rendement de la tomate. ABSTRACT The objective of this study is to evaluate the effects of the application of different organic fertilizers (manure, Balanites aegyptiaca (L.) Del., Boscia senegalensis (Pers.) Lam. ex Poir. and Sclerocarya birrea (A. Rich.) Hochst) on the growth and yield parameters of the F1 Mongal variety of tomatoes (Solanum lycopersicum L.) under semi-con controlled conditions. The study was conducted at the Gaston Berger University of Saint Louis farm in northern Senegal between April and june 2018. The experimental design used is randomized blocks with four (04) replicates, eight (08) treatments and three (03) doses (0.2%, 0.5% and 0.8%). The treatments applied are: T0 (control without fertilizer), T1 (Balanites aegyptiaca litter), T2 (Boscia senegalensis litter), T3 (Sclerocarya birrea litter), T4 (manure), T5, T6 and T7 (equal proportion of manure and each of the three (03) litters). After application of the various organic fertilizers, a decomposition time of 15 days was observed before sowing in 1.5 kg pots. After 60 days of growth, the results obtained showed that the effects on tomato growth vary according to the dose and quality of the organic matter supplied. B. senegalensis litter applied alone or in combination with manure and B. aegyptiaca litter used alone significantly improved some of the parameters studied (height, leaf area, aerial dry biomass and foliage color) at doses of 0.5% and 0.8%. The best effects were induced by the highest dose (0.8%) of B. senegalensis. S. birrea litter did not have significant effects on tomato growth and yield parameters. Manure showed no effect on tomato growth parameters compared to the control without fertilizer. Thus, the litter of B. senegalensis under the conditions of this trial showed great potential for improving tomato growth and yield parameters.

Les mares présentent un grand intérêt environnemental en raison des services écosystémiques qu'elles fournissent. Au Ferlo, les activités pastorales sont développées autour des mares. La connaissance des ressources herbacées est importante pour une gestion durable du pâturage autour des mares temporaires. L’objectif de cette étude est de déterminer la répartition spatiale des ressources herbacées autour des mares par une approche phytoécologique. L’échantillonnage sur des transects est réalisé dans les différents faciès morpho-pédologiques de deux mares pâturées et une mare non pâturée. La flore herbacée recensée compte 55 espèces, réparties dans 41 genres dont 22 familles. Les familles des Poacées et des Fabacées sont plus fréquentes quelle que soit l’unité morpho-pédologique et la mare, suivi de la famille des Cypéracées dans les mares et des versants et la famille des Zygophyllacées dont l’espèce Tribulus terrestris sur les dunes. Le recouvrement est globalement élevé (82,6%) dans la mare non pâturée et moyen sur les mares pâturées (55,33% et 46,4%). Au niveau des versants, les espèces sont de grandes tailles, rares et très diversifiées. Les espèces vivaces sont plus fréquentes autour des mares pâturées alors que les espèces rares se retrouvent autour de la mare non pâturée. Ces résultats révèlent ainsi l’influence prédominante des facteurs anthropiques et topographiques sur la répartition spatiale de la végétation herbacée.Mots clés : Transects, pâturée, phytoécologique, morpho-pédologiques. English Title: Distribution of herbaceous vegetation around temporary ponds: influence of anthropic and topographical factors in Widou Thiengoly (Ferlo, Northern Senegal)At the Ferlo, pastoral activities are developed around the ponds. The knowledge of herbaceous resources is important for sustainable grazing management around the temporary pools. The general objective of this study is to determine the spatial distribution of herbaceous resources around the ponds using a phytoecological approach. Transect sampling was carried out in the different morpho-pedological facies of two grazed ponds and one ungrazed pond. The recorded herbaceous flora includes 55 species, divided into 41 genera including 22 families. The Poaceae and Fabaceae families are more frequent whatever the morpho-pedological unit and the pond, followed by the Cyperaceae family in the ponds and on the slopes and the Zygophyllaceae family including the species Tribulus terrestris on the dunes. The overall coverage is high (82.6%) in the ungrazed pond and medium on the grazed ponds (55.33% and 46.4%). At the level of the slopes, the species are large, rare and much diversified. Perennial species are more frequent around the grazed ponds, while rare species are found around the ungrazed pond. These results thus reveal the predominant influence of anthropogenic and topographical factors on the spatial distribution of herbaceous vegetation.Keywords: Transect, grazed, phytoecological, morpho-pedological.

The general objective of this study is to describe the demographic structure and distribution according to topographic units of two woody species, Boscia senegalensis (Pers.) Lam. Ex Poir and Sclerocarya birrea (A. Rich) Hoscht in Widou Thiengoly (Ferlo) in northern Senegal. Stratified random sampling was used to carry out the study taking into consideration the topographic units (low background, pouring and tray). The ligneous inventory method consisted in carrying out vegetation surveys using a dendrometric approach with a minimum area of 2500 m2. The results obtained indicate that in the study area, the population of B. senegalensis is denser (42 ± 7.3 ind/ha) compared to that of S. birrea (6.1 ± 3.4 ind/ha). Topographic variability has a great influence on the life of the species. The study of the structure of individuals in diameter and height classes has shown that the population of B. senegalensis is shrubby and is generally renewed itself well, unlike that of S. birrea, which is more mature and whose lack of regeneration seems to compromise the renewal of the population. Given the total lack of regeneration of the species, this population, therefore requires more effective conservation strategies for its restoration.